A simple conceptual model for explaining how fruit trees work

The search for pomological understanding of fruit tree development and growth has been largely dominated by attempts to understand and/or explain responses and processes in trees by studying signaling molecules (hormones or plant growth regulators) that elicit different developmental and/or growth responses of various organs in trees. This approach to understanding fruit tree development and growth has tended to increase the complexity of the subject and largely ignores the fact that studying the presence or concentration of signaling molecules does not really address what controls how the signals are elicited or received. This approach has also tended to reinforce the idea that trees need to be understood as a unified whole, rather than the sum of their parts. It has been hypothesized for decades that plants grow as semiautonomous, interacting organs that compete for available resources at the whole plant level but that organs have their own genetically modulated controls that provide the basis for their development and growth. This hypothesis provides a simple alternative conceptual model for studying and understanding fruit tree development and growth. Thus, fruit trees can be understood by studying the behavior of individual organs and sub-organs (leaves, shoots, stems, branches, flowers/fruit, buds, roots) and the factors that govern how they function. This conceptual model does not negate the importance of signaling molecules in the regulating development and growth but recognizes a level of organ autonomy in developmental and growth processes and downplays the idea that these processes are governed at the whole plant level. Sub-models of development and growth of several types of organs as well as ideas for further studies will be presented.